A synthetic and theoretical study of the aggregation of amidoaluminium hydrides: Solid-state of the trimethylamine adduct [(Me3Si)₂NAl(Cl)(H) middot; NMe₃]

The amidoaluminium hydride complexes [(Me₃Si)₂NAl(X)(H) · NMe₃], X = H (1), Cl (2), were prepared by the metallation of bis(trimethylsilyl)amine by A1(X)(H)2 NMe3 (X = H and Cl]. The molecular structure of 2 as a inonomeric Lewis base adduct with four-coordinate aluminium centres and terminal amido groups was confirmed by X-ray crystal structure determination. We also find that bis(trimethylsilyl)amine forms a thermally stable adduct of alane, (Me₃Si)₂N(H) · A1H₃ (3). Ab initio molecular orbital calculations on the possible products arising from these reactions yielding 1 and 2 revealed that the amido-bridged species, {(μ-H₂N)A1(X)H}₂ (X = H and Cl), are favoured over nitrogen donor Lewis base adduct formation, H₂NA1(X)(H) · NH₃ (X = H and Cl), and then chlorobridged, {H₂NAl(μ-X)(H)}₂, (X = Cl only), and hydridobridged species, [H₂NAl(X)(μ-H))₂ (X = H and Cl).